What is a library?

As part of Chicago Ideas Week, Oct 12 – 18, 2015, the definition of library will include the L. To help commuters read more, and improve their access to books, the Chicago Transit Authority will leave books on the L trains. Travelers are encouraged to pick up the books, browse and read, but only until they reach their destination. They then must leave the books, and allow them to travel on their own for another commuter to discover and enjoy.

Do you commute via urban transit? What city would you like to see establish a similar projet?